Conventionally, it has been known to dip-form a dip-forming composition containing a latex of natural rubber to obtain a dip-formed article such as a nipple, a balloon, a glove, a medical balloon, a sack, or the like, which is used in contact with a human body. However, a latex of natural rubber contains proteins to cause an allergic symptom to a human body, and therefore has a problem as a dip-formed article in direct contact with the mucous membrane or organs of the body in some cases. Thus, consideration for using a synthetic isoprene polymer in place of the natural rubber has been made, and the use amount of the synthetic isoprene polymer has been increased year by year.
In order to cope with this situation, it is necessary to transport a large amount of a synthetic isoprene polymer latex. However, cost for transportation at a low concentrations is high, and therefore transportation at a concentration as high as possible has been demanded. However, a currently used synthetic isoprene polymer latex tends to rapidly increase viscosity around a solid content concentration of 62%, and accordingly there has been a limitation for making the concentration higher.
For example, Patent Literature 1 discloses a method for manufacturing a synthetic isoprene polymer latex, including dissolving a synthetic isoprene polymer in a solvent, emulsifying the synthetic isoprene polymer together with a surfactant, removing the solvent, and performing centrifugation. However, a latex manufactured by this method has a high viscosity at a high concentration, and therefore a trouble may occur, for example, the latex does not flow in an apparatus.